_{AUTHOR: Ola Wisniewska} 

A novel optical coherence tomography (OCT)-based physiological assessment, virtual flow reserve (VFR), has been shown to predict 2-year clinical outcomes following percutaneous coronary intervention (PCI), independent of anatomical measures like minimal stent area (MSA). This finding comes from a new substudy of the ILUMIEN IV trial, highlighting the potential of VFR to provide incremental prognostic information for assessing procedural success.¹

VFR is a novel technique that uses the detailed lumen geometry from an OCT image to compute a physiological assessment similar to fractional flow reserve (FFR). It models the vessel as a network of resistors to calculate pressure losses, providing a Pd/Pa ratio under simulated hyperaemic conditions without the need for a pressure wire or hyperaemic agents. The entire calculation adds less than a second to a standard OCT acquisition.

This post-hoc analysis used data from the ILUMIEN IV trial, a prospective, randomised controlled study comparing OCT-guided versus angiography-guided PCI.² This substudy included 2,057 patients who underwent single-lesion PCI and had a final OCT image available for retrospective VFR analysis. The primary endpoint was target vessel failure (TVF) at 2 years, a composite of cardiac death, target-vessel myocardial infarction (TV-MI), or ischaemia-driven target vessel revascularisation (ID-TVR). A key secondary endpoint was target lesion failure (TLF).

The median post-PCI VFR was 0.90. Notably, OCT-guided PCI resulted in a significantly higher VFR compared with angiography-guided PCI (0.90 vs 0.89; p<0.001). In a multivariable analysis, both lower VFR (per 0.1 unit increase: HR: 0.70; 95% CI: 0.0–0.95; p=0.021) and smaller MSA (per 1 mm² increase: HR: 0.84; 95% CI: 0.76–0.94; p=0.002) were independent predictors of 2-year TVF. For TLF, smaller MSA, lower VFR, and the presence of a proximal edge dissection were all independent predictors. The study found that a VFR value ≤0.90 was associated with poorer anatomical outcomes, including smaller stent expansion, more reference segment disease, and higher rates of dissection and malapposition.¹

These findings suggest that VFR provides prognostic information that is complementary to traditional OCT anatomical assessments. While MSA assesses the stented segment, VFR evaluates the entire vessel, offering a more comprehensive physiological picture of the procedural result. The authors concluded that "online VFR analysis can provide operators with an immediate assessment of post-PCI physiology in addition to OCT anatomy, providing incremental value in assessing procedural success and informing on clinical prognosis".¹ This dual assessment could help operators better identify suboptimal results and potentially improve long-term patient outcomes.

The authors suggest that further studies are warranted to evaluate the prospective use of combined OCT-derived anatomical and physiological guidance to determine if this approach can improve event-free survival after PCI.¹

References

1. Johnson TW, Bergmark BA, Croce K, et al. Impact of Optical Coherence Tomography-Based Post-PCI Physiology Assessment to Predict Clinical Outcomes: An ILUMIEN-IV Substudy. JACC. 2025;86(2):93–102. https://doi.org/10.1016/j.jacc.2025.05.019

2. Ali ZA, Landmesser U, Maehara A, et al. Optical coherence tomography–guided versus angiography-guided PCI. N Engl J Med. 2023;389:1466–1476. https://doi.org/10.1056/NEJMoa2305861

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